Bullseye puffer
Sphoeroides annulatus (bullseye puffer) is a species in the family Tetraodontidae, or pufferfishes. It is found in the eastern Pacific Ocean from California, USA to Pisco, Peru and the Galápagos Islands.
Sphoeroides annulatus has a moderately elongated body with a depth that is 25% to 33% of the standard length. Their back is olive-brown, and their flat ventral side is white. Their head and back have narrow yellowish lines, bars, and oblique bands, and 3 narrow bands behind the eyes. There is a double concentric oval on their back that resembles a ‘bullseye’, even though this may be obscure in large adults (Jenyns 1842). Their head, sides, and upper back are covered with small dark spots. They have a yellow iris and spotless fins.(Chávez Sánchez et al., 2008) Their head is large, projecting, and blunt and the gap between their elevated eyes is wide and convex. They have powerful, strong teeth. Their dorsal and anal fins are small with 6 to 9 rays with short bases, located farther back on their body with the anal fin being slightly behind the dorsal fin. Their caudal fin is bluntly convex, and they do not have pelvic fins. Their head and body are covered with small spines. Their skin is scaleless. They can grow to 48 cm in length (García-Ortega, 2008).
Globally, there are twenty-three species in the genus Sphoeroides. Of these eleven are found in Mexican waters, six in the Atlantic, and five in the Pacific Ocean. Three species of puffer span along the north-west of the Mexican Pacific coastline. Sphoeroides annulatus (Jenyns 1842), commonly known as the bullseye puffer, is distributed along the eastern Pacific Ocean, from south California, USA, to the Peruvian coasts, including the Gulf of California and Galápagos Islands (Fishbase).
Sphoeroides annulatus resides over sandy bottoms and occasionally around rocky reefs and adjacent sand patches. They use their habitat as camouflage from predators. They live in shallow depths but have been found up to 70 meters deep.(St-Louis, 2014) They can be found in subtropical and tropical temperatures averaging 25.8 °C.(Chávez Sánchez et al., 2008)
Sphoeroides annulatus are well camouflaged but may lack the ability to blow themselves up like other Puffers to prevent predator attacks. Like other Puffers, the Bullseye Puffer should be considered highly poisonous and even fatal, if eaten. This is due to the potential presence of the potent neurotoxins saxitoxin and/or tetrodotoxin, which is most likely found in their skin, viscera, and gonads and is believed to protect them from predation by larger fish.(Diggles et al., 2003) The presence of toxin content was determined in extracts of sperm, eggs, embryo, larval, post-larval, juvenile, pre-adult, and adult fish (Duncan et al., 2002).
Sphoeroides annulatus can ingest feed particles on the water surface, particles sinking in the water column, and resting on the bottom. Studies are in progress to evaluate the suitability of feeding either floating or sinking feed particles, or a combination of the two.(García-Ortega, 2008) This is based on species in aquaculture. This species feeds on insects, crustaceans, and small fish in the wild. They can use their beak like mouth to remove shellfish from their shells.
From a conservation perspective, Sphoeroides annulatus is currently considered to be of least concern. It has a stable, widely distributed population. They are a targeted species by subsistence fishermen off the beaches of Baja California Sur via hook and line and in certain locations can be caught in abundance. They are often encountered mid-water by divers. Their largest threat is habitat loss. (Chávez Sánchez et al., 2008).
Little information is known about the Sphoeroides annulatus role in the ecosystem. Sphoeroides consume insects, crustaceans, and small fish in shallow water. The juveniles are often found in mangroves and estuaries. (St-Louis, 2014)
